To fix below build error:
drivers/usb/host/built-in.o: In function `xhci_dwc3_remove':
drivers/usb/host/xhci-dwc3.c:174: undefined reference to `dwc3_shutdown_phy'
drivers/usb/host/built-in.o: In function `xhci_dwc3_probe':
drivers/usb/host/xhci-dwc3.c:130: undefined reference to `dwc3_setup_phy'
Signed-off-by: NKever Yang <kever.yang@rock-chips.com>